LED Lights

[Thistle]

Apologies that this is not boat-related but perhaps one of the electronics gurus on the forum could help.

I want to make up some circuits as shown below. No switch is necessary as on/off will be by connecting/disconnecting the PP3 6LR61 type battery. What I'm hoping is that someone will be able to suggest suitable resistors and green LEDs for me to use.


Many thanks.

 

[Alex_Blackwood]

Apologies that this is not boat-related but perhaps one of the electronics gurus on the forum could help.

I want to make up some circuits as shown below. No switch is necessary as on/off will be by connecting/disconnecting the PP3 6LR61 type battery. What I'm hoping is that someone will be able to suggest suitable resistors and green LEDs for me to use.
View attachment 141478

Many thanks.

How about something like these.
12v, 9v, 6v 5v Pre-Wired 5mm LED's Various Colours Pack of 5 | eBay

 

[VicS]

Apologies that this is not boat-related but perhaps one of the electronics gurus on the forum could help.

I want to make up some circuits as shown below. No switch is necessary as on/off will be by connecting/disconnecting the PP3 6LR61 type battery. What I'm hoping is that someone will be able to suggest suitable resistors and green LEDs for me to use.
View attachment 141478

Many thanks.

The value of the resistor (R), in ohms, can be calculated easily.

R = (9 - V_f ) / I_f

where V_f is the forward voltage across the LED , in volts, and I_f is the forward current, in amps.
The values of V_f and I_f can be found in the specification for the chosen LED

Calculate the required power rating of the resistor, in watts, from W = I² R, where I = I_f in amps
or just take it as W =9 x I_f
( Likely to be ¼ or ½ watt depending on the LED brightness )

You could buy the LEDs and resistors from RS Components or Rapid Electronics or from an eBay supplier of your choice. Round up the value of R to the nearest preferred value

 

[Thistle]

The value of the resistor (R), in ohms, can be calculated easily.

R = (9 - V_f ) / I_f

where V_f is the forward voltage across the LED , in volts, and I_f is the forward current, in amps.
The values of V_f and I_f can be found in the specification for the chosen LED

Calculate the required power rating of the resistor, in watts, from W = I² R, where I = I_f in amps
or just take it as W =9 x I_f
( Likely to be ¼ or ½ watt depending on the LED brightness )

You could buy the LEDs and resistors from RS Components or Rapid Electronics or from an eBay supplier of your choice. Round up the value of R to the nearest preferred value

That's very helpful. Many thanks.

 

[William_H]

The current for the I imagine little LEDs will depend on actual LED. try to get specs for the LED. Typical might be 50ma for small LED as in Christmas light type. Too much will destroy the LED too little will mean less than best light output. Power rating for the resistor will be current x voltage drop. Typically 6v by 50ma or 300mw which might mean you need something more than the tiniest resistor. ie go for 1w rating. ol'will

 

[Stemar]

Worth mentioning that driving an LED at a bit less than the specified voltage will vastly increase its life and, for a warning light type of thing, the loss of brightness should be unnoticeable.

 

[William_H]

Worth mentioning that driving an LED at a bit less than the specified voltage will vastly increase its life and, for a warning light type of thing, the loss of brightness should be unnoticeable.

Make that current not voltage ol'will